Oxygen narcotic?

[seeker242]

EAN32 is more narcotic than air.

Oxygen is more narcotic than nitrogen.

Choosing EAN32 to reduce narcosis will not work.

Splitting this off from another thread because of curiosity. I'm in the middle of doing a TDI trimix class, because helium! But one of the slides in the powerpoint we were shown, which I don't think was old, said "Most technical divers don't consider oxygen to be narcotic". Is that actually true? I have no idea myself personally but I was taught previously to treat it as if it is narcotic, so that's what I do. However, it seems that most dive planning software has an option to select yes or no, as to whether or not it's narcotic. What's up with the discrepancy? Why is there a discrepancy?

 

[kensuf]

A long time ago there was a belief that oxygen was not narcotic at all, and thus nitrox had reduced narcosis over air. Some people still believe that, I believe my NAUI instructor materials still have that statement.

OTOH, if you believe the Meyer-Overton hypothesis on which gases are narcotic, and how narcotic they are, you'll see oxygen (in theory) should be twice as narcotic as nitrogen. In reality, it's probably about the same because you're constantly metabolizing some of the oxygen. http://www.divegainesville.org/wp-content/uploads/2017/02/Narcosis-Meyer-Overton.pdf

At the end of the day, no one really understands why gases become narcotic or how the process of narcosis (or anesthetic) actually works. If you have some time, listen to the Radiolab story "Decoding the Void" in the Black Box episode. Black Box | Radiolab | WNYC Studios

 

[uncfnp]

If you leave Helium out of the mix, it seems that indeed oxygen is less narcotic under the conditions (partial pressures) encountered while diving.

Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox. - PubMed - NCBI

Hello,

To add to the mix, this has just been published.

Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox. - PubMed - NCBI

On balance, I favour the argument that oxygen is less narcotic at the pressures we can safely breathe because there is a substantial gap between inspired and tissue PO2 due to metabolism in the tissues that matter for a narcotic effect. In contrast, the gap between inspired and tissue tensions of nitrogen in the brain is almost zero because the brain is a very fast tissue. Having said that the functional difference in narcotic effect is probably quite small. If we really want to avoid narcosis, then breathing helium is the key.

Simon M

 

[Wookie]

I have no idea who the OP is, or if he ever came back, but he does present some research.....

Oxygen Narcosis

 

[leadduck]

here's a recent study from 2017 (in German): Refubium - Auswirkungen von Sauerstoff-angereichertem Atemgas auf Sporttaucher

They did dives for 25min at 25m, comparing air with EAN40 as bottom gas. Tests for memory and alertness showed that Nitrox makes a difference in narcosis.

"Conclusion This study shows both advantages and disadvantages using nitrox40. As disadvantages we can see the increasing peripheral pulmonary resistance und the decreasing elasticity of blood vessels. Advantages are the significantly reduced number of micro bubbles, a better received memory and alertness and the increased activity of the parasympathetic nervous system. Nitrox appears as a double-edged sword."

 

[Degenerate]

We were taught that oxygen is considered pretty narcotic in our Fundies class very recently, and I will continue to treat it as narcotic.
I don't have our papers on exactly how narcotic oxygen was compared to nitrogen, but I remember it was not something you should brush off your shoulder easily.

 

[martincohn]

Every single gas we breath underwater can kill ya. Don't believe it? FAFO

 

[Storker]

The conservative option is to regard O2 as being as narcotic as N2, so END=P(FO2+FN2). The liberal option is to regard only N2 as being narcotic, so END=P(FN2). I prefer the conservative option.

 

[helodriver87]

Narcosis is difficult to quantify. There's a lot more at play than just the gasses. Effort level, environmental conditions, day to day and individual variations, etc all factor in.

Narcotic potential as a function of lipid solubility is consistent and easily quantifiable. It's more conservative, but you can't control all the other factors.

 

[100days-a-year]

Some people are impaired @ .79 PPN and .21 PPO.Difficult to near impossible to quantify the degree of impairment from there on between individuals. Given the choice and money no object I prefer 02 to N. He adds to many variables in my diving to be worth it. So I stay relatively shallower.